There should be 2 or 4 weep holes on the unit. You will have to take off the shroud to gain access to them. you also may have to search around , the first time I had that happen on my last trailer ,it took me a while to find them. They are between 1/4" and 3/8" in diameter , and usually in or near the corners...
That would be my guess..
****ON EDIT - - - That is the outside shroud... You will need to be on the roof ,if your not comfortable with that , please find someone who is .
Good Luck ! Joe
2020 3991RD with-
17.5 Goodyear 114's , Titan Disc brakes, MorRyde 8K IS, Onan 6.5..